New London - An intriguing proposal at an early stage of consideration could enable the city to capture cheap, renewable energy stored underground, potentially providing heat and cooling to municipal and commercial buildings.

"It's before preliminary, if that's possible," said Tim Hanser, the city's public works director. "We are interested in finding alternative energy sources to reduce our carbon footprint and our energy costs."

The city has been approached by Mark Roberts, a New London resident and president of a Hartford-based workforce development firm, JDN Associates, about a plan that sounds almost too good to be true. With no upfront investment required on the part of this cash-poor city, schools and other municipal buildings would be retrofitted with geothermal energy systems that would reduce heating and cooling costs by 40 percent to 60 percent over oil- or natural gas-powered systems.

JDN would obtain financing to pay for the new system, and the city would pay the company for the heating and cooling provided through a 20-year contract that Roberts said would be significantly less than it currently pays. While the city would save money in the long run, JDN ultimately would turn a profit from the city's payments.

"JDN would handle all the financing of equipment and installation," Roberts said in an email message. "The city just signs an Energy Services Agreement to buy the energy at a much lower fixed rate. The city makes no capital investment. JDN does that."

The company, Roberts said, is preparing an estimate to install the system at C.B. Jennings Elementary School, an 80,000-square-foot building on Mercer Street, and one or more of the adjacent city buildings - the senior center, the school administration building and Bennie Dover Jackson Middle School - creating a geothermal district that could be expanded. At least 100,000 square feet of building space is needed for the project to be cost-effective, he said. The cost of a geothermal system for a 100,000-square-foot building would be roughly $1 million. Roberts said Jennings and surrounding buildings could be a pilot project showing the potential for retrofitting buildings downtown and in other parts of the city for geothermal, and that job training would be an important component.

"We want to build a local geothermal workforce," Roberts said in a phone interview.

Hanser said the city is preparing some information for JDN about current energy consumption at Jennings and nearby buildings. If the city decides to pursue the proposal further, it would have to issue a request for proposals and consider JDN's along with any others received, he said.

"Conceptually," Hanser said of the geothermal plan, "it's a great idea."

Waterford experience

While the city is a new acquaintance of the concept of geothermal energy, neighboring Waterford has embraced the technology. Four of the town's five schools have geothermal heating systems, the newest of them the 138,000-square-foot Waterford High School, which opened in April.

"It's the only way to go," said Jay Miner, director of buildings and grounds for the school system, as he opened the door of a room that houses the mechanical system for the high school. It's a sleek, bright, quiet space filled with water tanks, pipes and two rows of large metal boxes that contain the equipment that enables the system to harness the 54-degree ambient ground temperature 500 feet below the earth to produce warm or cool air for the building.

"These are the 10 reverse chillers, 30 tons each," said Miner.

The system, he explained, extracts heat from the ground through a network of 150 wells bored 500 feet under the school parking lot. In the winter, cold water circulates through pipes to the wells, where the temperature rises to that of the surrounding bedrock and soil. The water is then pumped back into the buildings, where heat pumps extract the energy of the warmed water to produce warm air for the building. In the summer months, the system works in reverse to cool the building. The main cost of running the system is the electricity required to run the heat exchange pumps.

"It's always got a heat source to extract the heat in the winter or a heat sink to get rid of the heat in the summer," Miner said. "And the system uses 100 percent outside air, so it's not stuffy and the CO2 levels are very low. It's very comfortable in the building."

The three elementary schools with geothermal systems, he said, are heated at a cost of about $3 per square foot - half the cost of the oil-fired boiler system at Clark Lane Middle School. Air filters on the systems must be changed twice daily, but other than that, he said, maintenance requirements have been relatively minimal.

"There is considerable upfront cost," he said, referring to the higher cost of equipment and installation for the geothermal systems, about one-third higher than an oil or natural gas system. "But we saw a return on our investment in 3½ years."

Miner emphasized that proper engineering of the wellfield is crucial to having a well-run system. Before construction, test wells had to be dug to determine the heat conductivity of the ground, and from there, a calculation of the number of wells was derived.

That same process was used when the geothermal system was designed that heats and cools New London Hall, the main science building at Connecticut College. A network of 45 wells, each about 500 feet deep, is buried under Temple Green, next door to the building. They capture or dissipate heat depending on the season, said James Norton, director of facilities management at Conn.

"It's been working great," Norton said. "It's a very efficient way to produce heat."

Retrofitting buildings

The geothermal systems at Conn College and Waterford schools were installed as part of new construction and major renovation projects, and probably wouldn't have been cost-effective on their own, both Miner and Norton said. The proposal in New London, however, would make use of a unique geothermal technology that can allow existing buildings to be retrofitted economically, according to Jim Moran, regional representative for a Michigan company, Advanced Energy Group, working with JDN.

The company uses equipment specially designed by Geothermal Innovations, a Brownsburg, Ind.-based company, to tap the heat of the earth more efficiently, reducing energy loss with pairings of crescent-shaped pipes. About a third fewer wells are needed to heat the same-sized building, Moran said, making the systems well-suited to urban areas with limited open space for well fields.

"We like to do large-scale commercial projects, whole districts," Moran said. "These are not quick and easy sales."

AEG recently completed a $1.25 million pilot project for four three-unit apartment buildings owned by Meriden Housing Authority that included overall renovations and installation of a geothermal heating and cooling system. Work on the next phase, 167 units, will start this spring, using an 11-member crew newly trained in geothermal installation, Moran said. A future phase will retrofit another 550 units, he added.

His company's website describes projects in Toledo, Dayton and other areas of the Midwest, including a citywide geothermal retrofit in Wyandotte, Mich., outside of Detroit. It is looking to expand into New England, and Moran, who grew up in Connecticut, began talking with cities large and small throughout his home state over the past year. Ultimately, that led to the agreement in Meriden.

After Roberts heard about the Meriden project, he approached Moran about working with JDN on a proposal for New London. Both emphasized that there is nothing in writing with the city.

Regardless of whether the idea progresses in New London, though, both large- and small-scale geothermal energy systems are becoming more common across the country. According to the U.S. Department of Energy, more than 5,000 megawatts of geothermal energy is in development, enough to power about 5 million homes. Another 2,500 megawatts of potential capacity is expected to be developed over the next decade. The systems in development include both the small-scale systems used for individual buildings, such as at the Waterford schools and at Connecticut College, and the large commercial-scale geothermal plants that tap hydrothermal formations mostly in the West.

j.benson@theday.com

Jay Miner, director of buildings and grounds for Waterford schools, tours the reverse chiller mechanical room Friday at Waterford High School. The room houses the geothermal equipment that heats and cools the school. A New London resident has proposed a similar system for the city.